The present invention relates to an analogue-to-digital converter capable of providing a digital signal representative of an input value consisting of an analogue electric signal. It is applicable every time it is necessary to provide a digital representation of a physical value susceptible of being measured by sensors, detectors or like pick-off transducers having an electric output. It is in particular usable in digital voltmeters and ammeters which display in a digital form the magnitude of a voltage or of a current. It is, however, of course, also usable when the digital output signal is applied to a complex processing system.
A great number of existing so-called A/D analogue-to-digital converters are adapted to make possible the display of the value of an input signal as a directly readable decimal number or the subsequent processing in the binary logic mode. Such analogue-to-digital converters are of several types the main ones of which are the successive approximation type, the single or double slope integration type and the stochastic type. These various kinds of converters has advantages and disadvantages, so that either one may be preferred depending on the prevailing requirement, for example, according to whether a short conversion time or a high resolution is essentially wanted. The known analogue-to-digital converters however exhibit common characteristic features which are inconveniences in many cases. The digital output signal is supplied in the form of a binary word having a number of significant bits which are provided in parallel, which number depends on the full-scale resolution. If it is desired to make the converter an integrated circuit, the integration density would increase exponentially with the number of significant bits, that is, with the resolution. The basic diagram would depend on the desired characteristics thereby causing compatibility problems when developing a system. With a given resolution, the cost price of the converter would increase very rapidly with the dynamic sought, for example, when changing from an eight-bit resolution to a sixteen-bit resolution.